Craig Symes

The importance of forest gardens as habitats for birds in Papua New Guinea

A project sponsored by the North of England Zoological Society. We acknowledge the support of RCF and Wildlife Conservation Society - PNG.

Principal investigators: Craig Symes and Dr Stuart Marsden


This seven month project examined the use of man-altered forest habitats by key frugivorous and insectivorous bird species in a hillforest site in PNG. The project was based in Crater Mountain Wildlife Management Area (CMWMA). A point count method was used to estimate bird densities in pristine and human-altered forests and detailed habitat recordings were taken at each point both to classify habitats, and to identify the habitat features which most influence use of different areas by individual bird species.

Background and Justification

The main threat to the majority of PNG's lowland birds is the alteration of forest both on a commercial scale through selective logging, and at a local level by indigenous people. Selective logging has received a good deal of attention in Asia and elsewhere (e.g. Thiollay 1992; Lambert 1992; Marsden 1998) but the ecological effects of different homegardening techniques are very poorly known for any region of the world (e.g. Thiollay 1995, Marsden et al. in press). Homegardens are a very common land use by indigenous people on PNG and involve the setting up of small plantations and other altered forests in which crops and important trees are grown at a small scale. This conversion by indigenous communities is extremely important in PNG, especially in the mid-altitude forests of the central highlands (Levett & Bala 1994). However, very little has been published on the impact of such practices on any of the region's wildlife, and this is frustrating as some homegarden regimes may be important habitats for the conservation of some bird species (Marsden & Pilgrim in press).

There is a clear lack of data on the response of New Guinea's birds to habitat alteration (Louman & Nicholls 1994) - 0ver 30% of bird species listed as 'Data-deficient' by Collar et al (1994) were from New Guinea (Mack & Wright 1996). There is particular concern that many frugivorous species in PNG may be increasingly threatened by forest alterations: PNG has 31 threatened and 32 near-threatened bird species (Collar et al. 1994; Mack & Wright 1998). Even fewer data are available for the region's insectivorous passerines, although the indication is that some tropical forest insectivores are severely affected by forest alteration (Bell 1982; Thiollay 1992; Mason 1996).

This project examines in a holistic way the response of different bird species to the mosaic of land uses produced in an area of central PNG. Different species may use various resources in primary and human-altered habitats at different times of the year. For example, a parrot species may rely on primary forest refuges for successful breeding, but also use home gardens for feeding at a time when primary forest fruit resources are scarce. By identifying precise species-specific needs, it may be possible to recommend minor changes to homegarden systems that will produce disproportional benefits to wildlife in terms of population densities and breeding success. The flagship species for the project will be Palm Cockatoo and other parrots such as Vulturine Parrot Psittrichas fulgidus, along with birds of paradise e.g. Cicinnurus spp. and other well-known species with serious conservation problems.

Our overall aims are to determine the factors affecting the ecological responses of key bird species to homegardening practices in CMWMA.

1. to use a point count distance sampling method to estimate population densities for a range of frugivorous and insectivorous birds in different homegarden regimes and adjacent pristine forest areas.

2. to compare the vegetation structure and species composition in different homegardens and adjacent pristine forest from detailed habitat readings taken at each census point.

3. to relate presence and use of individual points by different bird species to the vegetation characteristics of those points, and to those of adjacent points. In this way we will determine the importance of the spatial scale of the habitat mosaic produced by gardening practices.

4. To investigate more closely the ecology of birds in the different habitats/areas. This will include work on stratum usage, feeding resource use, movement and mixed-species flock dynamics to determine how these are influenced by different intensities of habitat alterations.

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Forest from the air


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Department of Environmental & Geographical Sciences

Dr Stuart J. Marsden
Applied Ecology Group
Telephone: 0161 247 6215
Facsimile: 0161 247 6318

Manchester Metropolitan University
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